Grr Vop Transparency Problem

[ziggx]

Hi there,

I created a testure vop that uses transparency -- only problem is when it casts shadows -- instead of getting a nice irregular shadow of the texture, I get the shadow of the underlying geometry.

I'm sure the solution is quite straightforward, it's just I can't see it.

Any help would be appreciated

[AndrewVK]

Switch shadow shader to "Filter Shadow" mode

[ziggx]

Duh! I KNEW it would be blindingly obvious. Thanks AndrewVK

[Visual Cortex Lab]

i know this problem has been already posted... but I'm out of my internet connection and I have no connection where I'm during last days... and "search" didnt gave me answers...

I'm almost breaking my head against the wall cause of Transparency shadow problem...

simple scene.. grid (floor), cube (a glass thin cube), light (point or cone..) with or without a VOP light (tried all of 'em) and shadow (tried both) shaders attached.

i simply CANNOT have the transparent shadow projected... just dark or dimmed (which is obviously not correct).. i cannot have the glass cast transparent shadows... where I am doing wrong???

I tried all shadowing types (filter, z, texture) and all shaders.. always same result.. plain shadows.

If i tint my glass in red.. i wasnt red transp shadow.. which i dont have. i dont have transp shadow at all.

I found really odd that this doesnt happens by default, i mean, I hope I dont have to write my own VEX code or VOP just to have basic transparent shadows.

thanks for your help.

[Jason]

Can you post up the scene? Even if you leave just the two objects and lights then we can look at it and tell you where you're going wrong.

[Visual Cortex Lab]

Can you post up the scene? Even if you leave just the two objects and lights then we can look at it and tell you where you're going wrong.

20665[/snapback]

I took a screenshot of the scene.. and aresulting render.

hope this helps a bit to show my problem.

the yellow cube have a VEX Glass shader.. the others just have a VEX plastic.

the Light gives me same results with no SHOP or with all VEX light shaders and VEX shadows shaders... what I cannot get is the Transparent Shadow that should be casted trought the glass cube.

Thanks for any help.

cheers.

[Jason]

[one,Aug 18 2005, 08:49 AM]the cube have a VEX Glass shader.. the others just have a VEX plastic.

One thing to be careful of with the VEX Glass shader - if you have *any* refraction setting in there, it'll block all light from passing through it. This is a basic shading rule because every ray passing through a refractive medium gets bent - i.e. redirected using the refraction equation. The only "true" way of rendering light passing though refractive mediums is to simuilate caustics.

If you replace the glass shader with a SuperMaterial shader and dial down the AlphaPara and AlphaPerp, you should get coloured light passing straight through. The VEX Glass shader should let light through too if your Refraction is set explicitly to 1. (And this is a conscious decision for the shader writer - to detect a refraction of 1 and then purposefully NOT raytrace the secondary ray and instead set the Of (opacity) to a non-opaque value.)

Does this make sense at all?

Jason

[Visual Cortex Lab]

One thing to be careful of with the VEX Glass shader - if you have *any* refraction setting in there, it'll block all light from passing through it. This is a basic shading rule because every ray passing through a refractive medium gets bent  - i.e. redirected using the refraction equation. The only "true" way of rendering light passing though refractive mediums is to simuilate caustics. 

If you replace the glass shader with a SuperMaterial shader and dial down the AlphaPara and AlphaPerp, you should get coloured light passing straight through.  The VEX Glass shader should let light through too if your Refraction is set explicitly to 1. (And this is a conscious decision for the shader writer - to detect a refraction of 1 and then purposefully NOT raytrace the secondary ray and instead set the Of (opacity) to a non-opaque value.)

Does this make sense at all?

Jason

20668[/snapback]

sorry i forgot to mention... refraction is set to 1.. cause I also tought that could be the problem.. but apprently it wasnt.

cheers

[Jason]

sorry i forgot to mention... refraction is set to 1.. cause I also tought that could be the problem.. but apprently it wasnt.

cheers

20669[/snapback]

Ah, I've just looked at the shader code for the VEX Glass shader and I see that the shader writer did NOT try to detect the case where refraction is set to 1. You'll see at the bottom of the shader that it always sets Of=1 - which means that the filterShadow shadow type will never have any other result for translucent shadows.

I think you're going to have to use the SuperMaterial shader for your particular task.